Combination electric and electronic ovens



' March 9, 1965 L. H. FITZMAYER 3,172,987

COMBINATION ELECTRIC ANS ELECTRONIC OVENS Filed Sept. 1, 1961 4 Sheets-Sheet l INVENTOR.

LOUIS H. FITZMAYER BY A T TO RNE Y8 March 9, 1965 H. FITZMAYER 3,172,987

COMBINATION ELECTRIC AND ELECTRONIC OVENS Filed Sept. 1. 1961 4 Sheets-Sheet 3 INVENTOR.

58 LOUIS H. FITZMAYER BY 61144747 59 W g 7 ATTORNEYS March 9, 1965 H. FITZMAYER 3,172,987

COMBINATION ELECTRIC AND ELECTRONIC OVENS Filed Sept. 1, 1961 4 Sheets-Sheet 4 FIG. 1/

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INVENTOR.

LOU/S H. FITZMAYER l6 0 I a 40 W Y ATTORNEYS United States Patent 3,172,987 COMBINATION ELECTRIC AND ELECTRONIC OVENS 'Louis H. Fitzmayer, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed Sept. 1, 1961, Ser. No. 135,582 22 Claims. (Cl. 219-10.55)

The present invention relates to electronic ovens and specifically to combined electric and electronic ovens, and more particularly to ultra-high frequency electromagnetic wave energy transmission and cooking platform constructions for such ovens.

It is a general object of the invention to provide in an electronic oven an improved transmission line of the type including a tubular outer conductor and an enclosed inner conductor for transmitting ultra-high frequency electromagnetic wave energy from a generator to the cooking cavity in the interior of the oven.

Another object of the invention is to provide in an electronic oven an improved transmission line of the type set forth including alternating sections, wherein the first and other odd numbered transmission line sections are of the type including a tubular outer conductor having a substantially circular cross section and an enclosed inner conductor having a substantially circular cross section, and wherein the second and subsequent even numbered transmission line sections are of the type including a tubular outer conductor having a susbtantially rectangular cross section and an enclosed inner conductor having a substantially rectangular cross section.

In connection with the foregoing object, it is another object of the invention to provide in an electronic oven an improved transmission line which is more easily and economically constructed. maintained and repaired, particularly when the transmission line includes a plurality of bends including right angle bends.

Yet another object of the invention is to provide in an upstanding electronic oven of the type having an upper boxlike metal liner including a top wall and defining a cooking cavity and a lower apparatus compartment containing a generator of ultra-high frequency electromagnetic wave energy, an improved distribution box mounted on the top wall which better distributes within the cooking cavity the electromagnetic wave energy transmitted thereto from the generator.

In connection with the foregoing object, it is another object of the invention to provide a combined electric and electronic oven having an improved arrangement of a distribution box mounted on the upper surface of the top wall thereof and cooperating with electric heating units of the resistance conductor type mounted on the lower surface of the top wall so as to achieve better electric and electronic cooking without interference one with the other.

A further object of the invention is to provide an improved electronic oven including a cooking cavity having a top wall supporting a distribution box thereon and a generator disposed beneath the cooking cavity with a transmission line including angularly disposed sections extending upwardly from the generator and substantially horizontally rearwardly and upwardly along the back of the cooking cavity and substantially horizontally across the top of the cooking cavity to the distribution box, there being substantially right angle connections between the transmission line sections extending substantially hori zontally and the transmission line sections extending upwardly.

Further features of the invention pertain to the particular arrangement of the parts and elements of the electronic oven, whereby the above-outlined and additional operating features thereof are attained.

3,172,987 Patented Mar. 9, 1965 The invention both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

FIGURE 1 is a side view with certain parts broken away of a combination electric and electronic oven embodying the present invention;

FIG. 2 is a fragmentary view in vertical section on an enlarged scale showing the interconnection between the magnetron, the lower vertical transmission line section and the lower horizontal transmission line section;

FIG. 3 is a side elevational view on an enlarged scale with certain parts broken away of the lower portion of the upper vertical transmission line section and the connection thereof to the lower horizontal transmission line section;

FIG. 4 is a view in vertical section through the lower horizontal transmission line section along the line 4-4 of FIG. 3;

FIG. 5 is a view in horizontal section through the upper vertical transmission line section along the line 5-5 of FIG. 3;

FIG. 6 is a view in horizontal section along the line 6-6 of FIG. 3;

FIG. 7 is an enlarged fragmentary view in vertical section illustrating the connection between the upper horizontal transmission line section and the distribution box;

FIG. 8 is a view in horizontal section along the line 8-8 of FIG. 7;

FIG. 9 is a side elevational view with certain parts in section illustrating the junction between the upper vertical transmission line section and the upper horizontal transmission line section;

FIG. 10 is a view in vertical section along the line 1tl-1tl of FIG. 9;

FIG. 11 is a fragmentary plan view of the top wall of the cooking cavity as seen in the direction of the arrows along the line 11-11 of FIG. 1;

FIG. 12 is a view in horizontal section, with certain portion broken away, as seen in the direction of the arrows along the line 1212 of FIG. 1 and illustrating the relationship between the cooking platform and the un derlying drip tray;

FIG. 13 is a fragmentary view in horizontal section along the line 13-13 of FIG. 1; and

FIG. 14 is a fragmentary view in perspective illustrating the construction of the cooking platform.

Referring to FIG. 1 of the drawings, the combination electric and electronic oven there illustrated and embodying the features of the present invention is generally designated by the numeral 10 and comprises an oven chamber or cooking cavity 11 defined by electrical conductive walls, and particularly by a box-like metal liner 12 including a top wall 13, a bottom wall 14, a rear wall 15 and two side walls 16, the front opening of the liner 12 being closed by a metallic oven door 17. The door 17 is provided with a hinge 17a and a handle 17b, whereby the door 17 can be moved between an open position and a closed position, suitable interlocking and switching apparatus (not shown) being provided to insure that there is no electromagnetic wave energy present within the cooking cavity 11 when the door 17 is in its open position.

Disposed below the upper cooking cavity 11 is an apparatus compartment within which is disposed a generator in the form of a magnetron 9%? which serves as a source of ultra-high frequency electromagnetic wave energy for the cooking cavity 11, the magnetron 99 being of conventional form and having, for example, an operating frequency of 915 megacycles. The electromagnetic amass? wave energy from the magnetron 9k) is transmitted to the cooking cavity 11 via a transmission line of the coaxial conductor type made in accordance with and embodying the principles of the present invention and including four sections 100, 2%, 360 and 4-00 connected in series and communicating with the interior of the cooking cavity 11 through a distribution box 59. More specifically, the magnetron 96 is disposed beneath the cooking cavity 11 and toward the rear thereof and is provided with a lower vertically extending transmission line section 100 of circular configuration connecting at a right angle with a lower horizontal transmission line section 2% of rectangular configuration which extends to a point below and to the rear of the rear wall 15 of the cooking cavity 11. The rear end of the transmission line section 2% is connected at a right angle to the lower end of an upper verti cal transmission line section 30%) of circular configuration which has the upper end thereof connected at a right angle to the rear end of an upper horizontal and forwardly extending transmission line section 4% of rectangular configuration having the front end thereof connected at a right angle to the distribution box The magnetron 90 is provided with a field coil housing 91 including a central cylindrical member providing a metallic tubular outer conductor 110 that is substantially circuiar in cross section and has disposed centrally thereof a metallic stud 150 connected to the output terminal of the magnetron 90 and spaced from the conductor 110 by insulators including an insulator 16%, the stud being substantially circular in cross section (see FIG. 2 also). The tubular outer conductor 110 and the enclosed inner conductor or stud 15% comprise the first section 1% of the transmission line interconnecting the magnetron 90 and the distribution box 50 mounted on the upper surface of the top wall 13 defining the cooking cavity 11.

In accordance With the present invention, it has been found that substantial and important advantages are obtained if the next or second section 200 of the transmission line connecting at right angles with the first section 1% is a transmission line section of rectangular configuration as illustrated in FIGS. 2 and 4 of the drawings. More specifically, the transmission line section 2th.) includes a inettllic tubular outer conductor 210 that is substantially rectangular in cross section as may be best seen from FIG. 4 of the drawings and includes wider upper and lower side walls 211 and 21?. joined by narrower side walls 213 and 214.

A readily separable connection between the transmission line sections 1% and 2% is desirable and to this end there is provided a metallic circular fitting 23th including a cylindrical side wall 231 having a normal external diameter slightly greater than the internal diameter of the tubular conductor 114i and slightly less than the Width of the wall 212, and further provided with longitudinal slots 232 thereon so that the fitting 234) can be inserted into the conductor lit and resiliently held therein. The upper end of the wall 231 has a portion 233 of reduced diameter extending through a circular opening H5 in the lower wall 212 of the outer conductor 27.9, the outer end of the portion 233 being turned over and crimped down as at 234 firmly to interconnect the fitting 23th and the tubular outer conductor 2155.

The end of the conductor 21h adjacent to the fitting 230 is closed by an end cap 22% having a flange 221 adapted to fit within the rectangular conductor 23.6, the end cap 220 being held in position by means of screws 222. Disposed Within the outer conductor 210 and enclosed thereby is a metallic inner conductor 25% which also has a rectangular cross section and is of ribbon-like configuration as can be best seen in FIG. 4 of the drawings, the inner conductor 25% being disposed centrally of the outer conductor 219 and with the fiat surfaces thereof substantially parallel to the side walls 211 and 212. The end of the inner conductor 25-3 adjacent to the magnetron 9% is mounted on the outer conductor 210 by means of a suitable insulating block 249 which is held in position by a screw 24-1 engaging the conductor 21! a screw 242 conmeeting the adjacent end of the inner conductor 250 with the insulating block 240 and also mounting thereon a resilient metallic connector or bullet Edi} which releasably and grippingly engages the stud 150. The resilient circular fitting 239 in combination with the connector 260 provides for ready assembly and connection of the second transmission line section 209 to the first transmission line section Hit) during construction and assembly, and further facilitates ready separation thereof during maintenance and repair.

As may be best seen in FIG. 1 of the drawings, the transmission line 299 extends rearwardly from the magnetron and the rear end thereof is closed by a metallic end cap 27b having an annular flange 271 therearound fittin into the interior of the conductor 216 and enclosing the rear end thereof, the end cap 270 being held in position by screws 272 (see FIG. 3 also). The rear end of the conductor 250 terminates a short distance from the end cap 27%) and is supported by an insulator block 280 held in position within the outer conductor 2th by means of a screw 28].. A threaded metallic stud 282 fixes the adjacent end of the inner conductor 2% on the insulator 28d and further supports a metallic stud 283 thereon which extends through a circular opening 216 provided in the top wall 211 of the outer conductor 21%. In order to provide a right angle connection and a readily separable connection 2% between the rear end of the transmission line sec tion Ztiti and the lower end of the transmission line sec tion 300, a metallic circular fitting 291 is provided having a diameter less than the Width of the Wall 211 and having a portion 2% of reduced diameter extending through the opening 216 and having the lower end thereof turned over and crimped as at 294, fixedly to mount the fitting 2% upon the upper wall 211 of the outer conductor 21%. Disposed about and grippingly engaging the outer surface of the circular fitting 291 is a cylindrical insulating sleeve 2% formed of any suitable insulating material, a preferred material being a synthetic organic plastic resin formed of tetrafluoroethylene polymers sold under the trademark Teflon, the insulating sleeve 295 extending beyond the upper end of the circular fitting 291 and having an external diameter substantially equal to the external diameter of the tubular outer conductor of the transmission line section 360, as will be explained more fully hereinafter. Surrounding the insulating sleeve 295 is a cylindrical metallic sleeve 2% which closely interfits with the sleeve 255 and extends substantially beyond the upper end thereof and has an internal diameter slightly greater than the external diameter of the tubular outer conductor of the transmission line section 3%, the upper end of the sleeve 2% being slotted to provide resilient ripping fingers thereon. Disposed upon the upper end of the stud 233 is an insulating washer 284 which may also be formed of tetrafiuoroethylene poiyrners, and disposed upon the upper surface of the washer 23- is a hollow metallic tube .337 having at the upper end thereof a connecting portion 239 of greater diameter. Disposed within the tube 287 is a metallic probe 285 threaded at the lower end thereof as at 286 and extending through the washer 284 and engaging a complementarily threaded opening in the stud 283. The upper end of the probe 285 has an insulating washer 238 formed, for example, of the tetrafiuoroethylene polymers disposed therein and provided with an outwardly extending flange resting upon the shoulder formed at the junction between the tube 287 and the connecting portion 28% at the upper end thereof. A screw extends through the washer 288 and engages the probe 285 to mount the parts in the assembled position illustrated in FIG. 3.

The construction of the transmission line section 3% which extends upwardly from the transmission line sec-- ductor 316 is provided having a cross section that is substantially circular, as can be best seen in FIG. 5, and disposed substantially concentric therewith is an enclosed metallic inner conductor 3569 which also has a substan-' tially circular cross section. The lower end of the outer conductor 31% is received Within the upper slotted end of the outer metallic sleeve 2% forming a part of the readily separable connection 290 and is in alignment with the circular fitting 291 which is in communication with and attached to the outer conductor 210. Although there is communication between the outer conductors 21d and 310 to facilitate the transmission of electromagnetic Wave energy therethrough, there is no D.C. connection therebetween, isolation being provided by the insulating sleeve 2%, whereby the relatively high D.C. potentials on the outer conductor 210 are not applied to the outer conductor 316, the outer conductor 31% in fact being grounded as will be explained more fully hereinafter. The lower end of the inner conductor 35% is provided with an enlargement 351 which is provided with slots 352 to facilitate insertion thereof into the connecting portion 289 on the upper end of the inner conductor 287. The parts thus described, including the lower end of the outer conductor 31% cooperating with the outer metallic sleeve 2% and the lower end 353]. of the inner conductor 350 cooperating with the connecting portion 289 of conductor 287, provide a readily separable connection which facilitates assembly and cliassembly of the transmission line sections 2% and 3M disposed substantially at a right angle with respect to each other.

The upper end of the transmission line section 3% is connected at a right angle to the rear end of the transmission line section dtitl. Referring to H68. 9 and of the drawings, it will be seen that the transmission line section 4% is provided with a metallic tubular outer conductor 41th which has a substantially rectangular cross section and includes wider upper and lower walls 411 and 412 connected along the edges thereof by vertically disposed side walls 413 and 414. Disposed within the outer conductor 410 and enclosed thereby is a metallic inner conductor 45% which also is rectangular in cross section and is disposed substantially centrally of the outer conductor 410 with the broadest surface thereof disposed substantially parallel to the top and bottom walls 411 and 412 of the outer conductor M0. The end of the outer conductor 41d disposed adjacent to the upper end of the transmission line section 309 is closed by an end cap 42 provided with an annurar flange which is adapted to fit within the outer conductor 410, the end cap 420 substantially filling and closing the outer conductor 110 and being held in position thereon by a screw 421. The adjacent end of the inner conductor 450 is supported within the outer conductor 41th on an insulating block 44d which is held in position upon the conductor 410 by means of a screw 441, a screw .42 connecting the adjacent end of the inner conductor 45% to the insulator 444i and also mounting thereon a metallic connector 443 which has slots thercaround providing spring fingers to grip and engage the upper end of the inner conductor 356 which extends through an opening sis in the lower wall 412 of the conductor 4-10. Also mounted within and extending through the opening 415 is a fitting generally designated by the numeral 430 and including a metallic cylindrical wall 431 having a plurality of slots therein forming spring fingers grippingly to engage and to make electrical contact with the adjacent end of the outer conductor 310. Integral with the cylindrical wall 431 is a cylindrical portion 433 of reduced diameter which extends through the opening 415 and is crimped over as at 434 to engage the bottom wall 412, of the conductor 410, thus to mount the fitting 431 within the opening 415 therein.

The other or front end of the transmission line section 4% is connected to the distribution box 50, the outer conductor 410 having an outturned flange 4st) extending therearound provided with openings therein to receive screws 461 theret-hrough. The adjacent end or" the inner conductor 450 is mounted upon the lower wall 412 on an insulating block 470 held in position thereon by a screw 4-71, a screw 472 extending through the inner conductor 450 and engaging the insulating block 470. The free end of the inner conductor 450 extends beyond the end of the outer conductor 410 and through an opening in the adjacent wall of the distribution box 50 and is provided with a downturned flange 451 connecting with an outwardly extending probe 452 disposed below but parallel to the main body of the inner conductor 450.

Referring particularly to FIGS. 1, 7 and 8 of the drawings, it will be seen that the distribution box 5th is formed of metal and includes a pair of elongated side walls 51 and 52 that are joined at the ends thereof by end Walls 54 and at the top by a top wall 53, the top wall 53 and the end walls 54 being mutually perpendicular to each other and to the side walls 51 and 52. Connection is made between the distribution box 559 and the transmission line section 405 through an opening 55 in the side wall 51 substantially midway of the ends thereof, as can be best seen in FIG. 8, and substantially midway vertically thereof, as can be best seen in FIG. 7. The opening 55 has a size and configuration like the interior of the outer con ductor tit) and a good electrical and sealing connection is made between the wall 51 and the outer conductor 410 by means of a braided metal gasket 4% disposed about the opening 55 and in contacting relationship with the outer conductor flange 160, the screws an passing through the flange 468, the gasket 4% and the wall 51 firmly to join these parts thus providing a grounding connection for the outer conductors 31d and 41b to the distribution box 50.

Extending outwardly from the bottom edge of each of the walls 51, 52 and 54 is a shoulder 57 which is adapted to receive a pane 71 of material which is impervious to oven gases but which is highly transparent to the electromagnetic wave energy a preferred material of construction being a fused mixture of powdered glass and mica sold under the trademark Mykroy. The lateral extent of the pane 71 is sufficient completely to cover the lower open side of the distribution box 5d and also to cover a window formed in the top Wall 13 of the liner l2 and defined by a depressed portion 18 and more specifically by an upturned flange 19 therearound so as to prevent oven gases from passing from the cooking cavity 11 into the distribution box 59. The depressed portion 18 supports a metal braid gasket '72 which serves to seal the opening on the bottom of the distribution box 56), the parts being held in the assembled position by screws 58 and providing a grounding connection from the distribution box St to the liner 12.

The distribution box 50 is disposed substantially centrally of the top wall 13 of the liner l2, i.e., it is disposed substantially midway between the front and rear of the liner 12 with the side Walls 51 and 52 disposed substantially paral el to the door 1'7 when in its closed position and with the end walls 54 disposed substantially equal distances from the adjacent side walls 16 of the oven liner 12. The length of the distribution box 56? i equal electrically to substantially one wave length of the electromagnetic wave energy ted thereto from the magnetron 9t As a result of the construction and positioning of the distribution box 5i) upon the top Wall 13, the electromagnetic wave energy from the magnetron 99 is advantageously distributed throughout the cooking cavity It to obtain the optimum operation thereof.

In order to provide means for tuning the magnetron 9t) and the transmission line to the cooking cavity ill thus to obtain more eificient utilization of the electromagnetic wave energy generated, means is provided for tuning the system, see particularly FIGS. 1, 2 and 8 of the drawings. A metallic tuning rod 75 is provided that is mounted in an opening 56 in the side wall 52 substantially centrally thereof tuning rod '75 and clamped thereto by means of a lock nut 76, the axis of the tuning rod 75 extending in general alignment with the axis of the body of the inner conductor 4-54 and over the offset probe 452 thereof. The tuning rod 75 extends beyond the side wall 52 and receives a second adjustment fitting 77, the lock nuts 76 and the adjustment fitting 77 permitting adjustable positioning of the tuning rod '75 with respect to the distribution box 50 and the inner conductor 45h, movement of the tuning rod 75 changing the capacity of the offset probe 452 on the inner conductor 4%.

As illustrated in the drawings, the appliance It? is a combination electric and electronic oven and includes a pair of spaced apart electric heating units of the sheathed resistance conductor type mounted on the lower surface of the liner top wall 13 and generally designated by the numeral 263, see FIGS. 1 and 11 of the drawings. The terminal mountings 21 for the heating units 2%) are preferably disposed to the left when viewed through the oven door 17 and the heating units 20 are generally rectangular and extend to the right substantially parallel to the oven door 17 and to the longitudinal axis of distribution box 5% one of the heating units 20 being disposed to the front of the distribution box Sit, i.e., toward the door 1'7, and the other heating unit 2t) being disposed to the rear of the distribution box it so that the heating units 24) do not interfere with the feeding of the electromagnetic wave energy from the distribution box 5% through the pane '71 into the cooking cavity 11.

A lower electric heating unit of the sheathed resistance conductor type is also mounted slightly above the bottom wall 14 of the liner l2 and is generally designated by the numeral so. The general configuration of the heating unit 6% can be seen in FIG. 13 of the drawings, the terminals 61 for the heating unit so extending through the rear wall 15 substantially midway between the side edges thereof and being spaced relatively close together. Heating unit sections 62 extend outwardly from the terminals 61 toward the side edges of the liner 12 and join with side section 63 disposed along the side walls 16 but spaced slightly therefrom, the side sections 63 connecting with a forward U-shaped section 64 interconnecting the side connections 63.

Disposed above the bottom wall i i of the liner l2 and also above the bottom heating unit 69 is a cooking platform generally designated by the numeral 36 (see FIGS. 1, l2 and 14) and including a central substantially imperforate metallic hub 31 from which extend radially outwardly a plurality of metallic rod-like arms 42 which carry thereon a floor 33 of metallic open-work construction, the outer ends of the arms 32 and the periphery of the fioor 33 carrying a circular upstanding metallic rim 34 thereon. Formed integral with the hub 31 and extending downwardly therefrom is an arbor 35 that fits into a bearing 36 mounted on the bottom wall 14 and containing a drive connection 81 for the arbor 35 to a drive unit fail mounted in the apparatus compartment 70, the drive unit 8t? being preferably an electric motor. Food to be cooked is placed upon the cooking platform 3th and the platform 36 is in turn driven by means of the drive unit so and the drive connection $1 and the arbor 35 at a rate of 6 revolutions per minute, for example, whereby to pass the food upon the platform 30 through the electromagnetic field within the cooking cavity ill so that various portions of the food being cooked are subjected to different field intensities, thereby equalizing the cooking thereof.

In order to collect the drippings and juices that are generated and which may fall from the cooking platform 3%, a drip tray generally designated by the numeral 40 is provided beneath the cooking platform 3% but above the electric heating unit so so as to protect the electric heating unit 64} from the drippings, see FIGS. 1 and 12 of the drawings. The drip tray 4d includes an outer metallic wire frame ill which extends therearound and which is adapted to hold the main portion of the drip tray 46} in proper operative position and to mount the drip tray 49 upon the usual embossments lea provided upon the side walls to of the liner 12. The body 42 of the drip tray 4% is formed of metal, is substantially flat and is provided around the outer periphery thereof with an upstanding and outwardly directed rim 4-3 attached to the frame ll and provided centrally thereof with an upstanding rim 44- around an opening therein which receives the arbor 35 therethrongh. The horizontal extent of the hub 31 is sufiicient so that it overlies the opening 5 in the drip tray so and directs drippings onto the upstanding rim 44 therearound so as to catch substantially all of the drippings from food on the cooking platform Ell in the drip tray 40.

From FEGS. 1 and 12 of the drawings, it will be seen that the bottom wall 14 of the liner 12 is substantially square and that the axis of the arbor 3-5 is disposed substantially centrally thereof and centrally with respect to the distribution box on the top wall 13. The diameter of the cooking platform 30 is only slightly less than the length of one side of the bottom wall 14 thereby providing a maximum area of support for food to be cooked. As has been noted above food placed on the cooking platform 3% will be rotated upon operation of the drive motor 8% so as to carry each portion of the food through field positions of varying strengths so as to obtain maximum utilization of the power injected into the cooking cavity 11 and so as more evenly and more thoroughly to cook the food upon the cooking platform 3%.

The dimensions of the drip tray 4* are such that it will catch substantially all of the drippings from the cooking platform 3t; as has been noted above, the hub 31 shielding the opening 45 from the drip tray 44 to prevent drippings falling upon the bearing 36 and the associated drive mechanism. The cooking platform 30 is readily clean in that the entire platform 30 with the arbor 35 attached can be removed by simply lifting the platform 3% upwardly and withdrawing it from the cooking cavity 11 through the opening provided by the oven door 17. The drip tray 4% is also removable with its associated frame 41 upon removal of the arbor 35 so as to permit ready cleaning thereof.

The drip tray so when in position performs the further function of shielding the lower electric heating unit 60 from the electromagnetic wave energy, the drip tray ll) being formed of metal and providing an effective choke for the wave energy throughout substantially the lower portion of the cooking cavity 11, whereby to prevent the formation of parasitic currents in the lower heating unit so, thereby protecting the heating unit 60 and preventing loss of electromagnetic wave energy therein. However, the side edges of the body 42 of the drip tray 4%) are spaced inwardly from the side walls 16 of the liner 12 to accommodate ready circulation of oven air over and into contact with the heating unit 60 disposed below the drip tray ll).

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications that fall within the true spirit and scope of the invention.

What is claimed is:

1. An electronic oven comprising upstanding structure defining a lower apparatus compartment and an upper box-like metal liner defining an upper cooking cavity, a generator disposed in said apparatus compartment for supplying ultra-high frequency electromagnetic wave energy, and a transmission line of the coaxial conductor type interconnecting said generator and said cooking cavity and including first and second sections disposed at an angle with respect to each other, whereby the electromagnetic wave energy is supplied into said cooking cavity via said transmission line from said generator, said first transmission line section including a first tubular outer conductor having a substantially circular cross section and a first enclosed inner conductor having a substantially cricular cross section, said second transmission line section including a second tubular outer conductor having a substantially rectangular cross section and a second enclosed inner conductor having a substantially rectangular cross section, one end of said first outer conductor abutting and joining a side wall of said second outer conductor and surrounding an opening provided therein and the adjacent end of said first inner conductor projecting through said opening and abutting and joining a side wall of said second inner conductor.

2. The electronic oven set forth in claim 1, wherein said second inner conductor is of ribbon-like configuration.

3. The electronic oven set forth in claim 1, wherein said first outer conductor joins said second outer conductor on a side wall thereof of greater width, and said first inner conductor joins said second inner conductor on a side wall thereof of greater width.

4. An electronic oven comprising upstanding structure defining a lower apparatus compartment and an upper box-like metal liner defining an upper cooking cavity, a generator disposed in said apparatus compartment for supplying ultra-high frequency electromagnetic wave energy, and a transmission line of the coaxial conductor type interconnecting said generator and said cooking cavity and including first and second sections disposed at an angle with respect to each other, whereby the electromagnetic wave energy is supplied into said cooking cavity via said transmission line from said generator, said first transmission line section including a first tubular outer conductor having a substantially circular cross section and a first enclosed inner conductor having a substantially circular cross section, said second transmission line section including a second tubular outer conductor having a substantially rectangular cross section and a second enclosed inner conductor having a substantially rectangular cross section, an outer circular fitting on one of the side walls of greater width or" said second outer conductor and surrounding an opening provided therein, an inner circular fitting on the adjacent side wall of greater width of said second inner conductor, a first readily separable connection between one end of said first outer conductor and said outer circular fitting, and a second readily separable connection between the adjacent end of said first inner conductor and said inner circular fitting.

5. The electronic oven set forth in claim 4, and further comprising an electrical insulator mounted in said second outer conductor in alignment with said opening therein and supporting the adjacent end of said second inner conductor and said inner circular fitting thereon.

6. An electronic oven comprising upstanding structure defining a lower apparatus compartment and an upper box-like metal liner defining an upper cooking cavity, a generator disposed in said apparatus compartment for supplying ultra-high frequency electromagnetic wave energy, and a transmission line of the coaxial conductor type interconnecting said generator and said cooking cavity and including first and second and third sections disposed at angles with respect to each other, whereby the electromagnetic wave energy is supplied into said cooking cavity via said transmission line from said generator, said first transmission line section including a first tubular outer conductor having a substantially circular cross section and a first enclosed inner conductor having a substantially circular cross section, said second transmission line section including a second tubular outer conductor having a substantially rectangular cross section and a second enclosed inner conductor having a substantially rectangular cross section, said third transmission line section including a third tubular outer conductor having a substantially circular cross section and a third enclosed inner conductor having a substantially circular cross section, said second transmission section extending from adjacent to said generator to the rear of said apparatus compartment, said first transmission line section having one end thereof connected to said generator and the other end thereof connected to one side of said second transmission line section adjacent to the front end thereof, said third transmission line section having one end thereof connected to the opposite side of said second transmission line section adjacent to the rear end thereof and having the other end thereof connected to said cooking cavity.

7. The electronic oven set forth in claim 6, wherein a decoupling insulator is provided in said third outer conductor to isolate the electrical potential on said second outer conductor from said cooking cavity.

8. The electronic oven set forth in claim 6, wherein the angle between said first transmission line section and said second transmission line section is substantially and the angle between said second transmission line section said third transmission line section is substantially 9. An electronic oven comprising upstanding structure defining a lower apparatus compartment and an upper box-l ke metal liner including a top wall and defining a cooking cavity, a metal distribution box supported upon said top Wall exteriorly of said cooking cavity and provided w th a bottom opening registering with a top window provided in said top wall, a generator disposed in said apparatus compartment for supplying ultra-high frequency electromagnetic wave energy, and a transmission line interconnecting said generator and said cooking cavity and including first and second sections disposed at an angle with respect to each other, whereby the electromagnetic Wave energy from said generator is transmitted v a said transmission line to said distribution box and is distributed from said distribution box through said bottorn opening and said window into said cooking cavity, said first transmission line section including a first tubular outer conductor having a substantially circular cross sectron and a first enclosed inner conductor having a substantially circular cross section, said second transmission line section including a second tubular outer conductor having a substantially rectangular cross section and a second enclosed inner conductor having a substantially rectangular cross section, one end of said first outer conductor abutting and joining a side wall of said second outer conductor and surrounding an opening provided therein and the adjacent end of said first inner conductor projectmg through said opening and abutting and joining a side wall of said second inner conductor, the end of said second outer conductor adjacent to said first outer conductor being closed and the other end of said second outer conductor abutting and joining a side wall of said distributron box and surrounding an opening provided therein and the adjacent end of said second inner conductor progctmg through said opening and into said distribution 10. The electronic oven set forth in claim 9, wherein said distribution box is of elongated form having a len th that is substantially equal electrically to one wave length of the electromagnetic wave energy.

11. The electronic oven set forth in claim 9, wherein said distribution box is of elongated form and said other end of said second outer conductor joins the side wall of said distribution box substantially midway between the ends thereof.

12. The electronic oven set forth in claim 9, and further comprising a tuning rod mounted on the side wall of said distribution box opposite said opening therein and electrically coupled to the adjacent end of said second inner conductor for tuning said generator to said cooking cavity.

13. The electronic oven set forth in claim 12, wherein said tuning rod is adjustable along its longitudinal axis so as to provide a variable position thereof with respect to the adjacent end of said second inner conductor in order to effect variable coupling therebetween for tuning said generator to said cooking cavity.

14. An electronic oven comprising an upstanding substantialiy box-like metal liner including a top wall and having a front opening and defining a cooking cavity, a metal front door cooperating with said liner and movable between open and closed positions with respect to said front opening, a metal distribution box supported upon said top wall exteriorly of said cooking cavity and provided with a bottom opening registering with a top window provided in said top wall, a transmission line of tie coaxial conductor type including an outer conductor and an enclosed inner conductor, one end of said outer conductor joining one of the walls of said distribution box in surrounding relation with an opening therein, the adjacent one end of said inner conductor projecting through said opening into the interior of said distribution box and constituting a probe disposed in spaced relation with the walls of said distribution box and located above said bottom opening, means including an ultra-high frequency generator operatively connected to the other end of said transmission line for supplying ultra-high frequency electromagnetic energy to said probe with said front door in its closed position, whereby ultra-high frequency electromagnetic wave energy is radiated from said probe and is distributed from said distribution box through said bottom opening and said window into said cooking cavity, and a pane supported in covering relation with respect to said window so as to prevent oven gases from passing from said cooking cavity into said distribution box, said pane being highly transparent to the electromagnetic wave energy that is distributed therethrough from said distribution box into said cooking cavity.

15. A combination electric and electronic oven comprising an upstanding substantially box-like metal liner including a top wall and having a front opening and defining a cooking cavity, a metal front door cooperating with said liner and movable between open and closed positions with respect to said front opening, a metal distribution box supported upon said top wall exteriorly of said cooking cavity and provided with a bottom opening registering with a top window provided in said top wall, means for supplying ulrta-high frequency electromagnetic wave energy into said distribution box with said front door in its closed position, whereby the electromagnetic wave energy is distributed from said distribution box through said bottom opening and said window into said cooking cavity, a pane suppolted in covering relation with respect to said window so as to prevent oven gases from passing from said cooking cavity into said distribution box, said pane being highly transparent to the electromagnetic wave energy that is distributed therethrough from said distribution box into said cooking cavity, an electric heating unit of the resistance conductor type and including two sections, and means for supporting the two sections of said electric heating unit in the upper portion of said cooking cavity adjacent to and somewhat below said top wall and respectively positioned outwardly on opposite sides of said window and thus out of the direct path of distribution of the electromagnetic wave energy from said distribution box into said cooking cavity.

16. The combination electric and electronic oven set forth in claim 15, wherein the two sections of said electric heating unit are supported from said top wall and are respectively positioned outwardly on the opposite front and rear sides of said window.

17. An electronic oven comprising an upstanding substantially box-like metal liner including top and bottom walls and a pair of side walls and a rear wall and having a front opening and defining a cooking cavity, a metal front door cooperating with said liner and movable between open and closed positions with respect to said front opening, a metal distribution box supported upon said top wall exteriorly of said cooking cavity and provided with a bottom opening registering with a top window provided in said top wall, an ultra-high frequency generator located below said bottom wall and exteriorly of said cooking cavity, a transmission line disposed exteriorly of said cooking cavity and interconnecting said generator and said distribution box, whereby the electromagnetic wave energy from said generator may be supplied via said transmission line into said distribution box and distributed therefrom through said bottom opening and said window into said cooking cavity, a pane supported in covering relation with respect to said window so as to prevent oven gases from passing from said cooking cavity into said distribution box, said pane being highly transparent to the electromagnetic wave energy that is distributed therethrough from said distribution box into said cooking cavity, said distribution box being electrically connected to said top wall, one end of said transmission line being electrically connected to said generator and the other end of said transmission line being electrically connected to said distribution box, and means including a decoupling insulator provided in said transmission line intermediate the ends thereof for isolating the electrical potential of said generator from said liner.

18. An electronic oven comprising an upstanding substantially box-like metal liner including top and bottom walls and a pair of said walls and a rear wall and having a front opening and defining a cooking cavity, a metal front door cooperating with said liner and movable between open and closed positions with respect to said front opening, a metal distribution box supported upon said top Wall exteriorly of said cooking cavity and provided with a bottom opening registering with a top window provided in said top wall, an ultra-high frequency generator located below said bottom wall and exteriorly of said cooking cavity, a transmission line disposed exteriorly of said cooking cavity and interconnecting said generator and said distribution box, whereby the electromagnetic wave energy from said generator may be supplied via said transmission line into said distribution box and distributed therefrom through said bottom opening and said window into said cooking cavity, and a pane supported in covering relation with respect to said window so as to prevent oven gases from passing from said cooking cavity into said distribution box, said pane being highly transparent to the electromagnetic wave energy that is distributed therethrough from said distribution box into said cooking cavity, said generator being located beneath said bottom wall and forwardly of said rear wall, said transmission line including first and second and third sections, said first transmisison line section being disposed substantially horizontally and below said bottom wall and being connected adjacent to the front end thereof to said generator, said third transmission line section being disposed substantially horizontally and above said top wall and being connected adjacent to the front end thereof to said distribution box, said second transmission line section being disposed in upstanding position and rearwardly of said rear wall, the lower end of said second transmission line section being connected to said first transmission line section adjacent to the rear end thereof, and the upper end of said second transmission line section being connected to said third transmission line section adjacent to the rear end thereof.

19. The electronic oven set forth in claim 18, wherein said transmission line is of the coaxial conductor type including an outer conductor and an enclosed inner conductor.

20. An electronic oven comprising an upstanding substantially box-like metal liner including top and bottom walls and a pair of side walls and a rear wall and having a front opening and defining a cooking cavity, a metal front door cooperating with said liner and movable between open and closed positions with respect to said front opening, a metal distribution box supported upon said top wall exteriorly of said cooking cavity and provided with a bottom opening registering with a top window provided 13 in said top wall, an ultra-high frequency generator located below said bottom wall and exteriorly of said cooking cavity, a transmission line disposed exteriorly of said cooking cavity and interconnecting said generator and said distribution box, whereby the electromagnetic wave energy from said generator may be supplied via said transmission line into said distribution box and distributed therefrom through said bottom opening and said window into said cooking cavity, and a pane supported in covering relation with respect to said window so as to prevent oven gases from passing from said cooking cavity into said distribution box, said pane being highly transparent to the electromagnetic wave energy that is distributed therethrough from said distribution box into said cooking cavity, said transmission line being of the coaxial conductor type including an outer tubular conductor and an enclosed inner conductor, said transmission line comprising at least four series connected sections, each odd one of said transmission line sections including a tubular outer conductor having a substantially circular cross section and an enclosed inner conductor having a substantial- 1y circular cross section, and each even one of said transmission line sections including a tubular outer conductor 1 having a substantially rectangular cross section and an enclosed inner conductor having a substantially rectangular cross section.

21. The electronic oven set forth in claim 14, wherein said distribution box is of elongated form and extends substantially parallel to and above the top of said front opening.

22. The electronic oven set forth in claim 21, wherein said distribution box is located substantially centrally of said top wall.

References Cited in the tile of this patent UNITED STATES PATENTS 2 519,750 Ehlers Aug. 22, 1950 2,630,489 Beck et a1 Mar. 3, 1953 2,748,239 Long et al. May 29, 1956 2,782,292 Long Feb. 19, 1957 2,881,695 Di Pietro Apr. 14, 1959 2,925,028 Haynes et al. Feb. 16, 1960 2,929,905 Hahn Mar. 22, 1960 2,961,520 Long Nov. 22, 1960 

14. AN ELECTRONIC OVEN COMPRISING AN UPSTANDING SUBSTANTIALLY BOX-LIKE METAL LINER INCLUDING A TOP WALL AND HAVING A FRONT OPENING AND DEFINING A COOKING CAVITY, A METAL FRONT DOOR COOPERATING WITH SAID LINER AND MOVABLE BETWEEN OPEN AND CLOSED POSITIONS WITH RESPECT TO SAID FRONT OPENING, A METAL DISTRIBUTION BOX SUPPORTED UPON SAID TOP WALL EXTERIORLY OF SAID COOKING CAVITY AND PRO VIDED WITH A BOTTOM OPENING REGISTERING WITH A TOP WINDOW PROVIDED IN SAID TOP WALL, A TRANSMISSION LINE OF THE COAXIAL CONDUCTOR TYPE INCLUDING AND OUTER CONDUCTOR AND AN ENCLOSED INNER CONDUCTOR, ONE END OF SAID OUTER CONDUCTOR JOINING ONE OF THE WALLS OF SAID DISTRIBUTION BOX IN SURROUNDING RELATION WITH AN OPENING THEREIN, THE ADJACENT ONE END OF SAID INNER CONDUCTOR PROJECTING THROUGH SAID OPENING INTO THE INTERIOR OF SAID DISTRIBUTION BOX AND CONSTITUTING A PROBE DISPOSED IN SPACED RELATION WITH THE WALLS OF SAID DISTRIBUTION BOX AND LOCATED ABOVE SAID BOTTOM OPENING, MEANS INCLUDING AN ULTRA-HIGH FREQUENCY GENERATOR OPERATIVELY CONNECTED TO THE OTHER END OF SAID TRANSMISSION LINE FOR SUPPLYING ULTRA-HIGH FREQUENCY ELECTROMAGNETIC ENERGY TO SAID PROBE WITH SAID FRONT DOOR IN ITS CLOSED POSITION, WHEREBY ULTRA-HIGH FREQUENCY ELECTROMAGNETIC WAVE ENERGY IS RADIATED FROM SAID PROBE AND IS DISTRIBUTED FROM SAID DISTRIBUTION BOX THROUGH SAID BOTTOM OPENING AND SAID WINDOW INTO SAID COOKING CAVITY, AND A PANE SUPPORTED IN COVERING RELATION WITH RESPECT TO SAID WINDOW SO AS TO PREVENT OVEN GASES FROM PASSING FROM SAID COOKING CAVITY INTO SAID DISTRIBUTION BOX, SAID PANE BEING HIGHLY TRANSPARENT TO THE ELECTROMAGNETIC WAVE ENERGY THAT IS DISTRIBUTED THERETHROUGH FROM SAID DISTRIBUTION BOX INTO SAID COOKING CAVITY. 